Method and apparatus to automatically search data carriers, such as RFID tags and machine-readable symbols

ABSTRACT

A data carrier reader is capable of executing a number of different reading methods. A method for reading single RFID tags can store read data to a buffer for eventual transmission to a host, and can suppress redundant data. Still another method associates data read from an RFID tag with a particular object or item using a data coded in a machine-readable symbol. In a further method, the machine-readable symbol is automatically read when the RFID tag is within a predetermined proximity of the reader. In each method, the data carrier reader provides the user a consistent and intuitive output to identify the successful and unsuccessful operations such as reading an RFID tag or machine-readable symbol.

TECHNICAL FIELD

This application relates to methods and apparatus for reading datacarriers such as machine-readable symbols (e.g., barcode symbols, areaand/or matrix code symbols) and wireless memory devices (e.g., RFIDtags).

BACKGROUND OF THE INVENTION

A variety of methods exist for tracking and providing information aboutitems. For example, inventory items typically carry printed labelsproviding information such as serial numbers, price, weight, and size.Some labels include data carriers in the form of machine-readablesymbols that can be selected from a variety of machine-readablesymbologies, such as bar code, and/or area or matrix code symbologies.The amount of information that the symbols can contain is limited by thespace constraints of the label. Updating the information in thesemachine-readable symbols typically requires the printing of a new labelto replace the old label.

Data carriers such as memory devices provide an alternative method fortracking and providing information about items. Memory devices permitthe linking of large amounts of data with an object or item. Memorydevices typically include a memory and logic in the form of anintegrated circuit (“IC”) and means for transmitting data to and/or fromthe device. For example, a radio frequency identification (“RFID”) tagtypically includes a memory for storing data, an antenna, an RFtransmitter, and/or an RF receiver to transmit data, and logic forcontrolling the various components of the memory device. RFID tags aregenerally formed on a substrate and can include, for example, analog RFcircuits and digital logic and memory circuits. The RFID tags can alsoinclude a number of discrete components, such as capacitors,transistors, and diodes.

RFID tags can be passive, active or hybrid devices. Active devices areself-powered, by a battery for example. Passive devices do not contain adiscrete power source, but derive their energy from an RF signal used tointerrogate the RFID tag. Passive RFID tags usually include an analogcircuit that detects and decodes the interrogating RF signal and thatprovides power from the RF field to a digital circuit in the tag. Thedigital circuit generally executes all of the data functions of the RFIDtag, such as retrieving stored data from memory and causing the analogcircuit to modulate the RF signal to transmit the retrieved data. Inaddition to retrieving and transmitting data previously stored in thememory, the RFID tag can permit new or additional information to bestored in the RFID tag's memory, or can permit the RFID tag tomanipulate data or perform some additional functions. RFID tags areavailable from a number of manufacturers, including Texas Instruments,Dallas, Tex., and Omron of Japan.

Another form of memory device is an optical tag. Optical tags aresimilar in many respects to RFID tags, but rely on an optical signal totransmit data to and/or from the tag.

Additionally, touch memory data carriers are available, for exampletouch memory devices from Dallas Semiconductor of Dallas, Tex. Touchmemory devices are similar to RFID tags but require physical contactwith to store and retrieve data.

A user typically secures a data carrier to an item, such as a good,product, or container by way of a pressure sensitive adhesive. The datacarrier often encodes information specifically relating to the item suchas identifying or destination information. An individual, such as acheckout or inventory clerk, can retrieve data about any given item, forexample, by scanning the machine-readable symbol or interrogating the RFtag, optical tag, or touch memory device. Access to the data can beuseful at the point of sale, during inventory, during transportation, orat other points in the manufacture, distribution, sale, or use of thetagged item.

Relatively high cost is one of the drawbacks of memory devices, thus,many applications rely on the less expensive printed machine-readablesymbols. Another significant drawback is the difficulty of identifying aparticular memory device from a group of memory devices. It isparticularly difficult to associate the information read from the RFIDtag with a physical item or container. The ability to read data fromdifferent types of data carriers, for example machine-readable symbolsand RFID tags, and/or to associate and manipulate such data can providenumerous benefits in the automatic data collection (“ADC”) industry.

SUMMARY OF THE INVENTION

In one aspect a data carrier reader includes an RFID tag reading sectionand a machine-readable symbol reading section, which can contain somecommon components. The reader is operable in an RFID tag reading modeand/or a symbol reading mode. The reader provides a consistent andintuitive user interface within, and between, the operating modes. Theuser interface can include visual, aural and tactile indicators. Thevisual indicators can include a pattern displayed by indicators on thereader, or projected onto or near the data carrier.

In another aspect, a data carrier reader is capable of executing anumber of different reading methods. A method for reading single RFIDtags can store read data to a buffer for eventual transmission to ahost, and can suppress redundant data. Another method identifies allRFID tags having a characteristic data string that appears on a list. Incontrast, another method identifies any RFID tags having acharacteristic data string that does not appear on the list. Stillanother method associates data read from an RFID tag with a particularobject or item using a data coded in a machine-readable symbol. In afurther method, the machine-readable symbol is automatically read whenthe RFID tag is within a predetermined proximity of the reader. In eachmethod, a consistent and intuitive output can be provided to the user toidentify the successful and unsuccessful operations such as reading anRFID tag or machine-readable symbol.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, identical reference numbers identify similar elementsor acts. The sizes and relative positions of elements in the drawingsare not necessarily drawn to scale. For example, various elements may bearbitrarily enlarged and positioned to improve drawing legibility.

FIG. 1 is a partial block diagram, partial front elevational view of afacility including a data carrier reader reading data carriers carriedby a number of items, the reader communicate with a host through aninterface.

FIG. 2 is a functional block diagram of the reader according to oneembodiment of the invention.

FIG. 3 is a top plan view of the reader of FIG. 2.

FIG. 4 is a partial top plan view of an alternative set of visualindicators for the reader of FIG. 2.

FIGS. 5A-5C together form a chart of selected input and output signalsfor operating the reader of FIG. 2 and the visual indicators of FIG. 4.

FIG. 6 is a top plan view of a graphic display of the reader of FIG. 3.

FIG. 7 is a top plan view of an alpha-numeric display of the reader ofFIG. 3.

FIG. 8 is a flowchart showing a method of reading single RFID tags.

FIG. 9 is a flowchart showing a method of determining when a reader isfinished reading RFID tags.

FIG. 10 is a flowchart showing a method of reading multiple RFID tags.

FIG. 11 is a flowchart showing a method of performing an inclusivesearch of RFID tags.

FIG. 12 is a flowchart showing a method of performing an exclusivesearch of RFID tags.

FIG. 13 is a flowchart showing a method of associating data from an RFIDtag with an item using a machine-readable symbol.

FIG. 14 is a flowchart showing a method of automatically imaging amachine-readable symbol based on proximity to an RFID tag to associatedata from an RFID tag with an item using the machine-readable symbol.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various embodiments of theinvention. However, one skilled in the art will understand that theinvention may be practiced without these details. In other instances,well-known structures associated with RFID tags, RFID tag readers, one-and two-dimensional symbologies, symbol readers, microprocessors andcommunication networks have not been shown or described in detail toavoid unnecessarily obscuring descriptions of the embodiments of theinvention.

The headings provided herein are for convenience only and do notinterpret the scope or meaning of the claimed invention.

Data Carrier Reader

FIG. 1 shows a data carrier reader 10 reading one or more of a number ofdata carriers, such as the RFID tags 12 on the containers or items 14.The reader 10 includes a head 16, a handle 18 and a trigger 20. Aninterface 22 can couple the reader 10 to a host 23, such as acentralized computer, as described in detail below.

The tags 12 can take the form of an RFID tag 12A that carries amachine-readable symbol 24A on a visible surface of the tag.Alternatively, the tags 12 can take the form of a separate RFID tag 12Band machine-readable symbol 24B. The separate RFID tag 12B andmachine-readable symbol 24B can be physically associated, for example,securing each to the same physical object, such as the item 14. The RFIDtag 12A, 12B and machine-readable symbol 24A, 24B can contain logicallyassociated information, for example information related to the item 14to which the tags 12 are secured, such as identifying and/or shippinginformation.

As shown in FIG. 2, the reader 10 contains an RFID tag reading section30, a symbol reading section 32, a user input section 34, a user outputsection 36, and a communications section 38 all coupled by a bus 40. Thebus 40 provides data, commands and/or power to the various sections30-38. The reader 10 can include an internal power source such as arechargeable battery (not shown) or can receive power from an externalpower source such as a wall outlet by way of an electrical cord (notshown). Each of these sections 30-38 will be described individuallybelow, although in the illustrated embodiment some of these sectionsshare common components.

RFID Tag Reading Section

FIG. 2 shows the RFID tag reading section 30 of the data carrier reader10 including an antenna 42 coupled to a radio 44. The radio 44 iscoupled via the bus 40 to a microprocessor 46 and a random access memory(“RAM”) 48. The RAM 48 can include a characteristic data string buffer49 to temporarily store characteristic data strings, as will beexplained in detail below. Alternatively, the reader 10 can include adiscrete characteristic data string buffer (not shown). While FIG. 2shows a single microprocessor 46, the data carrier reader 10 may includeseparate dedicated processors for each of the RFID tag and symbolreading sections 30, 32.

While a dipole antenna 42 is shown, the data carrier reader 10 canemploy other antenna designs. Of course, the antenna can be selected toachieve a particular focus, for example, a highly directional antennacan enhance the ability of the reader 10 to select a single RFID tag 12out of a group of RFID tags. The radio 44 can take the form of atransceiver capable of transmitting and receiving at one or more of thefrequencies commonly associated with RFID tags 12 (e.g., 350 kilohertz,400 kilohertz, 900 kilohertz). While these frequencies typically fallwithin the radio frequency range of the electromagnetic spectrum, theradio 44 can successfully employ frequencies in other portions of thespectrum. Antenna design and radios are generally discussed in The ARRLHandbookfor Radio Amateurs, 76^(th) Ed., American Radio Relay League,Newington, Conn., U.S.A. (1999) (ISBN: 0-87259-181-6), and commonlyassigned patent application U.S. Ser. No. 09/280,287, filed Mar. 29,1999, entitled ANTENNA STRUCTURES FOR WIRELESS COMMUNICATIONS DEVICE,SUCH AS RFID TAG (Atty. Docket No. 480062.648).

A read only memory (“ROM”) 50 stores instructions for execution by themicroprocessor 46 to operate the radio 44. As used in this herein, ROMincludes any non-volatile memory, including erasable memories such asEEPROMs. The programmed microprocessor 46 can control the radio 44 toemit an interrogation signal, including any required polling codes orencryption, and to receive a return signal from an RFID tag 12A, 12B.The programmed microprocessor 46, RAM 48, radio 44 and antenna 42 thusform the RFID reading section 30.

Symbol Reading Section

FIG. 2 also shows the symbol reading section 32 of the data carrierreader 10 including an image sensor 52 and an illumination source, suchas the laser 53. The image sensor 52 can take the form of a one- ortwo-dimensional charge coupled device (“CCD”) array. Alternatively, thereader 10 can employ other known imaging devices, for example laserscanners or Vidicons. In certain embodiments, the data carrier reader 10can omit the illumination source, for example where the image sensor 52is a two-dimensional CCD array operable with ambient light.Alternatively, the data carrier reader 10 can rely on other illuminationsources, such as light emitting diodes (“LEDs”) or a strobe light, thatcan be positioned to illuminate a desired one of the machine-readablesymbols 24A, 24B. The reader 10 can employ suitable optics such as lensand mirrors (not shown) for directing light reflected from themachine-readable symbol 24A, 24B to the image sensor 52.

The reader 10 includes an analog-to-digital (“A/D”) converter 54, totransform the analog electrical signals from the image sensor 52 intodigital signals for use by the microprocessor 46. The bus 40 couples theimage data from the A/D converter 54 to the microprocessor 46 and theRAM 48. A portion of the RAM 48 can form an image buffer 56 fortemporarily storing data, such as a captured image data from the imagesensor 52. The ROM 50 contains instructions for the microprocessor 46,that permit the microprocessor 46 to control the image sensor 52 tocapture image data and to decode and/or manipulate the captured imagedata. The programmed microprocessor 46, RAM 48, image sensor 52, and A/Dconverter 54, thus form the symbol reading section 32.

Symbol reading and decoding technology is well-known in the art and willnot be discussed in further detail. Many alternatives for image sensors,symbol decoders, and optical elements that can be used in the reader 10are taught in the book, The Bar Code Book, Third Edition, by Roger C.Palmer, Helmers Publishing, Inc., Peterborough, N.H., U.S.A. (1995)(ISBN 0-911261-09-5).

Communications Section

The communications section 38 includes a communications buffer 47 and acommunications port 49. The communications buffer 47 can temporarilystore incoming and outgoing data and/or commands where thecommunications speed of the reader 10 does not match the communicationsspeed of some external device, such as the interface 22 (FIG. 1). Thecommunications port 49 provides communications between the reader andexternal devices. While shown as a hardwire connection to the interface22 (FIG. 1), the communications port can be a wireless interface, andcan even employ the antenna 42 and radio 44 of the RFID tag readingsection 30. Additionally, the reader 10 can include the interface 22 asan integral part of the reader 10.

The interface 22 (FIG. 1) can provide communications over acommunications network 68 to the host 23, allowing transmissions of dataand/or commands between the reader 10 and the host 23. Thecommunications network 68 can take the form of a wired network, forexample a local area network (“LAN”) (e.g., Ethernet, Token Ring), awide area network (“WAN”), the Internet, or the World Wide Web (“WWW”).Alternatively or additionally, the communications network 68 can be awireless network, for example, employing infrared (“IR”), satellite,and/or radio frequency (“RF”) communications.

The host 23 can receive from each of a number of the readers 10, datacollected from the RFID tags 12 and machine-readable symbols 24. Thehost 23 can use the data with a database, and can automaticallymanipulate the data, for example to automatically performing inventoryor to track shipments.

The host 23 can provide data and commands to each of a number of thereaders 10. For example, the host can share data between the readers 10,such as providing a list of either located or missing identifiers, aswill be discussed in more detail below in reference to inclusive andexclusive searches. The host 23 can provide a command to toggle thereader 10 between an RFID tag reading mode and a symbol reading mode,which is described below in further detail. Thus, the host 23 cancommand, coordinate and share data between a number of readers 10.Commonly assigned patent application U.S. patent application Ser. No.09/401,066, filed Sep. 22, 1999, entitled, “SYSTEM AND METHOD FORAUTOMATICALLY CONTROLLING OR CONFIGURING A DEVICE, SUCH AS AN RFIDREADER” contains teachings that can be used to automatically control orconfigure the reader 10.

User Input Section

The user input section 34 includes the trigger 20, the mode switch 34,and can include a user input device 58. The bus 40 couples the modeswitch 34 to the microprocessor 46. In response to selection of the modeswitch 34, the microprocessor 46 switches between the symbol readingmode and the RFID tag reading mode, for example by toggling between thetwo operating modes. The reader 10 can employ additional operatingmodes, or switching positions as desired, for example a switch positionthat places the reader 10 in an OFF state or a WAIT state to conserveenergy.

In the symbol reading mode, the microprocessor 46 operates the imagesensor 52 to image one of the machine-readable symbols 24A, 24B. Themicroprocessor 46 decodes the imaged symbol to retrieve the data encodedin the machine-readable symbol 24A, 24B, such as a respectiveidentifier. In the RFID tag reading mode, the microprocessor 46 operatesthe radio 44 to emit an interrogation signal and to receive a responsefrom one or more of the RFID tags 12A, 12B to the interrogation signal.The microprocessor 46 decodes the response signal to retrieve the dataencoded in the RFID tag 12A, 12B, such as a respective identifier.

The mode switch 34 can be a membrane switch, mounted to the exterior ofthe reader 10 for easy selection by the user. The mode switch 34 canadditionally, or alternatively, be implemented in the software tosupplement or replace the user selectable mode switch on the exterior ofthe reader 10. The software implemented switch is particularly usefulwhere the host 23 (FIG. 1) controls the operating mode of the reader 10.Alternatively, the mode switch 34 can be implemented as an icon on atouch sensitive display 74. In further alternatives, the trigger 20 canfunction as the mode switch 37. In one instance, the number ofsuccessive trigger pulls or activations can determine the operatingmode. For example, two successive trigger pulls can select the symbolmode, while three successive trigger pulls selects the RFID mode; or asingle trigger pull can cause the reader 10 to read a symbol while adouble trigger pull toggles between the symbol and RFID modes.Alternatively, the duration of trigger activation can determine theoperating mode. For example, a trigger pull of under 0.5 seconds canselect the symbol mode, while a trigger pull of longer than 0.5 secondscan select the RFID mode; or a trigger pull of under 0.5 seconds cancause the reader 10 to read a symbol while a trigger pull of over 0.5seconds toggles the reader between the symbol and RFID modes.Additionally, or alternatively, the mode switch can be contextsensitive, switching modes based on data read from a previously readdata carrier 12A, 12B, 24A, 24B. For example, a previously read RFID tag12A can indicate the existence of a symbol 24A. In response, the datacarrier reader 10 can automatically switch into symbol mode and read thesymbol 24A associated with the RFID tag 12A.

The bus 40 also couples the trigger 20 to the microprocessor 46. Inresponse to activation of the trigger 20, the microprocessor 46 cancause the image sensor 52 to image one of the machine-readable symbols24A, 24B when the reader 10 is operating in the symbol reading mode. Inat least one embodiment, the microprocessor 46 can also cause the radio44 and antenna 42 to emit an interrogation signal in response to theactivation of the trigger 20 while in the reader 10 is operating in theRFID tag reading mode.

The user input device 58 can take the form of a keypad 60 (FIG. 3),mouse, touch screen and/or other user operable device to inputinformation and/or commands to the reader 10. The bus 40 couples theuser input device 58 to the microprocessor 46, to allow the user toenter data and commands.

User Output Section

The user output section 36 includes human-perceptible visual and audioindicators 62, 64 respectively. The bus 40 couples the visual and audioindicators 62, 64 to the microprocessor 46 for control thereby. Thevisual indicators 62 can take a variety of forms, for example: lightemitting diodes (“LEDs”); a graphic display such as a liquid crystaldisplay (“LCD”), and/or an alpha-numeric display such as a 7-segmentdisplay. The audio indicator 64 can take the form of one or moredynamic, electrostatic or piezo-electric speakers 66. The speaker 66 isoperable to produce a variety of sounds (e.g., Clicks and Beeps), and/orfrequencies (e.g., tones), and to operate at different volumes. Thereader 10 can also include tactile indicators such as a vibratingmember. The specific operation of the user output section 36 isdiscussed in more detail below.

FIG. 3 shows a portion of the user interface located on the head 16 ofthe reader 10. The user interface includes the elements of the userinput section 34, such as the trigger 20, the mode switch 34 and thekeypad 60. The user interface also includes the elements of the useroutput section 36 including the visual indicators 63 and the speaker 66.In particular, the visual indicators 62 in the illustrated embodimentinclude a set of RFID related LEDs 70, a set of machine-readable symbolrelated LEDs 72, and a display 74.

The data carrier reader 10 can additionally, or alternatively, employthe laser 53 as the visual indicator. The laser can be successivelypulsed or flashed according to a set of predefined human-recognizabletemporal patterns to provide information to the user, such as userindications corresponding to the various reader operations and/or theresponses from the date carriers 12A, 12B, 24A, 24B. Employing the laser53 as a portion of the user interface provides a number of distinctbenefits. For example, operating the laser 53 to providehuman-recognizable patterns can eliminate the need for other visualindicators 62. The data carrier reader 10 can employ multipleillumination sources such as lasers 53 or LEDs of different colors, oran illumination source capable of producing a number of different colorsto provide the appropriate user indications, as set out in FIGS. 5A-5C.As discussed in detail below, the human-recognizable patterns can takethe form of a predefined sequence of laser flashes of one or morecolors, separated by time (i.e., temporal pattern).

The visual and audio indicators 62, 64 are configured to provide anintuitive user interface consistent across the RFID tag and symbolreading modes. For example, the RFID tag related and symbol related LEDsets 70, 72 each contain green 76, 78, yellow 80, 82 and red 84, 86LEDs, in an order or pattern that is consistent between the sets. Theparticular LED 76-86, as well as the number and/or pattern of flashes,is set such that the same color LEDs flash the same pattern foranalogous RF tag reading and symbol reading activities. For example, theyellow LED 80 in the RFID tag related set 70 flashes during the readingof one of the RFID tags 12A, 12B (FIG. 1), while the yellow LED 82 inthe machine-readable symbol related set 72 flashes during the reading ofone of the machine-readable symbols 24A, 24B (FIG. 1). The reader 10responds to a successful read of the RFID tag 12A, 12B ormachine-readable symbol 24A, 24B by illuminating the corresponding greenLED 76, 78, respectively, for a set period of time such as 5 seconds.The red LEDs 84, 86 can indicate unsuccessful or incomplete operations.The user receives visual feedback, where the color, position andsequence of the visual indicators 62 is consistent within, and acrossthe RFID tag and symbol operating modes. Consistent feedback can reducetraining time and costs, and can lead to more efficient operation of thereader 10.

Similar to the visual indicators 62, the speaker 66 provides consistentfeedback within and across the operating modes. In the illustratedembodiment, the speaker 66 emits a “beep” or a “click” sound, althoughthe speaker 66 can emit different and/or additional sounds. The speaker66 can emit, for example, a single beep each time either an RFID tag12A, 12B or a machine-readable symbol 24A, 24B is successfully read.When searching a field of RFID tags 12A, 12B for one or more particulartags, the speaker 66 can emit a click for each non-match and a beep foreach match.

The user interface can also include an ON/OFF indicator 97, and/or a LowPower indicator 99 to identify the operating condition of the reader 10.

FIG. 4 shows an alternative set of visual indicators for the reader 10.This alternative embodiment, and those alternative embodiments and otheralternatives described herein, are substantially similar to previouslydescribed embodiments, and common acts and structures are identified bythe same reference numbers. Only significant differences in operationand structure are described in detail below.

The reader 10 of FIG. 4 employs only three LEDs to simplify switchingwhile providing the human-perceptible visual indications. A two stateLED serves as the machine-readable symbol related indicator 87. Themachine-readable symbol indicator 87 produces no light in an OFF stateand a Green light in an ON state. A three state LED serves as the RFIDrelated indicator 89. The RFID related indicator 89 produces a Greenlight in first ON state, a Yellow light in second ON state, and NO lightin an OFF state. A two state LED serves as the ON/OFF indicator 97. TheON/OFF indicator produces a Yellow light, or No light. The ON/OFFindicator is proximate the machine-readable symbol related and RFIDrelated indicators 87, 89. In FIG. 4, the mode switch 34 takes the formof a toggle or slider switch, having a neutral position (center), asymbol mode position (left of center) and an RFID mode position (rightof center). The positions are consistent with the corresponding visualindicators 87, 89, respectively.

FIGS. 5A-C describe a variety of input and outputs signals for thereader 10, and particularly for the audio indicator 64 and laser 53 ofFIG. 2, and for the visual indicators 87, 89, 97 of FIG. 4. While thetable is self-explanatory, a brief description of the columns follows.Column 31 defines a reader status or error conditions corresponding toreader activities. Column 33 describes the operation of the visualindicators 87, 89, 97 of FIG. 4, in response to the various readerstatus or errors conditions. Similarly, column 35 describes theoperation of the audio indicator 64 in response to the various readerstatus or error conditions 33. Column 37 describes the operation of thelaser to produce the desired human-recognizable patterns correspondingto the various reader status or errors conditions 31. Column 39describes messages for display on the display 74 corresponding to thevarious reader status or errors conditions 31. Column 41 describesPDT/Host messages corresponding to the various reader status or errorsconditions 31. Column 43 describes data and/or error codes sent to thehost 33, corresponding the various reader status or errors conditions31. As discussed above, these user indications provide a consistentinterface for the user within and across the operating modes, permittingthe user to efficiently operate the reader 10.

The display 74 can additionally, or alternatively, provide the userother visual indications. For example, a graphical display 88 (FIG. 6),can employ a first set of icons 90 to indicate RFID tag activities and asecond set of icons 92 to indicate symbol reading activities. (Note,typically only a single icon will be displayed at a time, althoughmultiple icons are shown in FIG. 6 for the convenience of thisdescription.) For example, screen icons 81, 83 and 85 can represent RFIDreading, successful reading of the RFID tag 12A, 12B, and unsuccessfulreading of RFID tag 12A, 12B, respectively. Similarly, screen icons 91,93 and 95 can represent machine-readable symbol reading, successfulreading of the machine-readable symbol 24A, 24B, and unsuccessfulreading of the machine-readable symbol 24A, 24B, respectively.

Similarly, an alpha-numeric display 94 (FIG. 7) can employ a first setof words 96 to indicate RFID tag activities and a second set of words 98to indicate symbol reading activities. (Again, typically only a singleword will be displayed at a time, although multiple are shown in FIG. 7for the convenience of this description.) The display 94 isself-explanatory and in the interest of brevity will not be furtherdescribed. Other visual indications, as well as audio and tactileindications are of course possible.

Selected Methods of Operation

Different methods of operating the reader 10 or a reader having similarcapabilities are disclosed below. As set out in the below methods, theintuitive and consistent operation of the user interface within andacross operating modes can provide numerous benefits. While severalmethods are set out for illustration, other methods employing similartechniques are within the scope of the invention. Also, the followingdescriptions employ certain descriptions of user outputs (e.g., Beep,Click, Red LED, Yellow LED, and Green LED) for convenience ofdescription. Those skilled in the art will appreciate that other sounds,colors, visual, tactile indications, and/or other human-perceptibleindications could be used.

Single Tag Read Mode

FIG. 8 shows a method 100 of reading RFID tags 12A-12B (FIG. 1)employing the reader 10 (FIGS. 1-3). Turning on the reader 10, orswitching into the RFID tag reading mode, can automatically cause themicroprocessor 46 to start the method 100 in step 102. Alternatively, oradditionally, the user can cause the microprocessor 46 to start the RFIDtag reading method 100 by selecting an appropriate key from the keypad60 or icon from the display 74. Upon starting in step 102, themicroprocessor 46 can perform an initialization process, for exampleloading appropriate operating instructions from the ROM 50 to the RAM48, initializing the characteristic data string buffer 49 and/orperforming a series of systems checks on the various component andsubsystems of the reader 10, as set out in step 104.

Under the instructions loaded in the RAM 48, the microprocessor 46activates the radio 44 in step 106. In step 108, the radio 44 receivesdata from the RFID tags 12A, 12B. The radio 44 can emit an interrogationsignal to cause the RFID tags 12A, 12B to respond, or, the radio 44 cansimply receive signals from RFID tags 12A, 12B that emit signals withoutinterrogating the RFID tags. A variety of passive, active and hybridRFID tags 12A, 12B are known in the art and will not be discussed infurther detail. A discussion of RFID tags can be found in commonlyassigned patent applications: U.S. Ser. No. 09/173,539, filed Oct. 15,1998, entitled WIRELESS MEMORY DEVICE AND METHOD OF MANUFACTURE (Atty.Docket No. 480062.630); U.S. Ser. No. 09/164,203, filed Sep. 30, 1998,entitled MEMORY TAG AND METHOD OF MANUFACTURE (Atty. Docket No.480062.632); U.S. Ser. No. 09/173,137, filed Oct. 15, 1998, entitled RFTAG HAVING STRAIN RELIEVED STIFF SUBSTRATE AND HYDROSTATIC PROTECTIONFOR A CHIP MOUNTED TIIERETO (Atty. Docket No. 480062.635); and U.S. Ser.No. 09/164,200, filed Sep. 30, 1998, entitled CHIP PLACEMENT ON SMARTLABELS (Atty. Docket No. 480062.642).

In step 110, the microprocessor 46 determines whether duplicate tag datashould be suppressed. If suppressed, previously read or acquired datawill not be stored or reported a second time. Suppression can be a userselection, or can be a selection transferred from the host 23, or can bepreset, for example by the reader manufacturer or owner. If suppressionis not active, the reader 10, in step 112, automatically transmits theread data, for example to the host 23, and provides an indication to theuser that the data has been received and transmitted. To provide theindication, the reader 10 activates the speaker 66 to emit a single“beep” and activates the Green RFID related LED 76 for a short time, insteps 114, 116, respectively. Control passes to an end of the routine100, in step 118.

If suppression is active, the microprocessor 46, compares acharacteristic data string from the received data to othercharacteristic data strings stored in the characteristic data stringbuffer 49, in step 120. The characteristic data string can be any stringof characters stored in the RFID tags 12A, 12B that permit the reader 10to determine whether a particular RFID tag 12A, 12B has been read morethan once. For example, the characteristic data string can be a uniqueidentifier programmed into each of the RFID tags 12A, 12B.Alternatively, the characteristic data string can be the entire set ofdata stored in the RFID tag 12A, 12B, or can be any subset or field ofdata recognizable by position, offset, delimiter or other such fieldidentifier. The microprocessor 46 branches at step 122 based on thedetermination of whether the received characteristic data stringcorresponds, or matches, any of the stored data strings.

If the received characteristic data string corresponds to, or matches,any of the stored characteristic data strings, the reader 10 provides anindication that the RFID tag 12A, 12B has been read again, activatingthe speaker 66 to emit a single “click” and activating or “flashing” theRed RFID related LED 84 in steps 124, 126, respectively. Themicroprocessor 46 determines in step 128, if the reader 10 is finishedreading RFID tags 12A, 12B, as described in detail below.

If the received characteristic data string does not correspond to, ormatch any of the stored data strings, the microprocessor 46 updates thecharacteristic data string buffer 49 containing the read characteristicdata strings, for example storing the newly received characteristic datastring to the buffer 49 in step 130. The reader 10 can automaticallytransmit the read data in step 132, for example to the host 23 (FIG. 1).The reader 10 also provides an indication that a new RFID tag 12A, 12Bhas been read (e.g., read for the first time since the buffer 49 wasinitialized), activating the speaker 66 to emit a “beep” in step 134 andactivating the Green RFID related LED 76 in step 136. Control passes tothe end of the routine 100 in step 118.

FIG. 9 is a flowchart of a method 200 of determining when a reader 10 isfinished reading. The microprocessor 46 can execute this method 200 inplace of each step labeled “DONE” in the various other methods, such asat step 128 of FIG. 8 (discussed above), or in the other Figures(discussed below). As set out in the Figures, the method 200, startingat step 202, acts as a function or subroutine, returning a Boolean value(e.g., TRUE/FALSE, YES/NO, or DONE/NOT DONE conditions). While themethod 200 could be implemented as an integral part of the other methodsdiscussed herein, it is set out separately for ease of discussion.

At step 240, the microprocessor 46 determines whether the trigger 20 hasbeen released. A trigger release indicates that the user is finishedreading. If the trigger 20 has been released, the microprocessor 46 setsthe Boolean value to “DONE” at step 242, and passes control to an end ofthe routine 200 at step 218, returning the appropriate Boolean value.For example, when returning to the method 100 (FIG. 8), the condition“DONE” can cause the reader 10 to stop interrogating RFID tags 12A, 12B.

If the trigger 20 has not been released, the microprocessor 46 in step244 determines whether a timeout condition has been exceeded. Forexample, the reader 10 can assume that all RFID tags 12A, 12B have beenread if a new (e.g., not previously read) tag is not found after somelength of time or some number of consecutive repeatedly read RFID tags12A, 12B. While the length of time or number of repeated reads can bepreset, the length or number of repeats can also be determined duringthe reading, for example as a function of RFID tag density (e.g., numberof RFID tags per unit time). The microprocessor 46 can rely on aninternal clock or a separate clock circuit (not shown) in measuring thetimeout period. Employing RFID tag density to calculate the stoppingcondition “on the fly” reduces the likelihood of ending a searchprematurely.

If the timeout condition is exceeded, the reader 10 considers reading tobe finished, sets the Boolean value to “DONE” at step 242, and passescontrol to the end of the method 200 at step 218, producing theappropriate Boolean value for determining the next operation, such asturning the radio OFF. If the timeout condition is not exceeded, themicroprocessor 46 determines whether a stop command has been receivedfrom the host 23 in step 246. If a stop command has been received, theBoolean value is again set to “DONE” at step 242, and control passes tothe end of the method 200 at step 218. If a stop command has not beenreceived from the host 23, the microprocessor 46 at step 248, determineswhether all RFID tags 12A, 12B have been read. If all RFID tags 12A, 12Bhave been read, the Boolean value is set to “DONE” at step 242 andcontrol passes to the end of the method 200 at step 218, returning theappropriate response. If all RFID tags 12A, 12B have not been read, theBoolean value is set to “NOT DONE” at step 250 and control passes to theend 218, thereby returning the appropriate Boolean value.

Multi Tag Read/Write Modes

FIG. 10, shows an additional, or alternative embodiment of operatingunder the present invention. Similar steps in the methods are assignedreference numerals that have the two least significant digits in common(e.g., the “Start” step is respectively numbered: 102, 202, 302, . . . ,702 in FIGS. 6-12, respectively).

FIG. 10 shows a method 300 of reading multiple RFID tags 12A, 12B(FIG. 1) employing the reader 10 (FIGS. 1-3). In a similar fashion tothe method 100, the microprocessor 46 starts executing the method 300 atstep 302, initializing the reader 10 at step 304, turning ON the radio44 in step 306, and receiving responses from the RFID tags 12A, 12B instep 308. In step 320, the microprocessor 46 compares a characteristicdata string from the received data to other characteristic data stringsstored in the characteristic data string buffer 49 to determine whetherthe reader 10 has read the particular RFID tag 12A, 12B before. Themicroprocessor 46 branches at step 322 based on the determination ofwhether the received characteristic data string corresponds, or matches,any of the stored data strings.

If the received characteristic data string corresponds to, or matches,any of the stored characteristic data strings, the microprocessor 46adds the read characteristic data string to the characteristic datastring buffer 49, at step 330. The reader 10 provides an indication thatthe read RFID tag 12A, 12B has been previously read, activating thespeaker 66 to emit a single “click” and activating or “flashing” the RedRFID related LED 84 at steps 352 and 354, respectively. In step 356, themicroprocessor 46 examines a counter (“Retry”) to determine whether amaximum number of iterations has been exceeded without finding a “new”(e.g., not previously read) RFID tag 12A, 12B. If the number ofiterations without encountering a new RFID tag 12A, 12B has beenexceeded, control passes to an end of the method 300 at step 318. If thenumber of iterations without encounter a new RFID tag 12A, 12B has notbeen exceeded, the microprocessor 46 increments the Retry counter instep 358, and determines in step 328 whether the reader 10 is finishedreading RFID tags 12A, 12B, as described in detail above with respect tomethod 200 (FIG. 9). The microprocessor 46 returns to receiving RFID tagresponses in step 308, or passes control to the end of the method 300 atstep 318 based on the Boolean value returned by the method 200 (FIG. 9).

If the received characteristic data string does not correspond to, ormatch any of the stored data strings, the microprocessor 46 resets theRetry counter in step 360, and adds the read characteristic data stringto the characteristic data string buffer 49 in step 362. The reader 10in step 364, automatically transmits the read data, for example to thehost 23. The reader 10 also provides an indication that a new RFID tag12A, 12B has been read (e.g., read for the first time since the buffer49 was initialized), activating the speaker 66 to emit a “beep” in step314 and activating the Green RFID related LED 76 in step 316. Themicroprocessor 46 determines in step 328 whether the reader 10 isfinished reading RFID tags 12A, 12B, as described in detail above withrespect to method 200 (FIG. 9). The microprocessor 46 returns toreceiving RFID tag responses in step 308 or passes control to the end ofthe method 300 in step 318 based on the condition returned by the method200.

The data carrier reader 10 can employ a method that includes operating aradio 44 in the RFID tag interrogator 30 to write to an RFID tag 12A,12B; and producing a first human-perceptible indication after writing tothe RFID tag 12A, 12B. The method can also include receiving aconfirmation signal from the RFID tag 12A, 12B prior to producing thefirst human-perceptible indications. Further, the method can includewriting to a number of other RFID tags 12A, 12B; producing the firsthuman-perceptible indication after writing to each of the other RFIDtags 12A, 12B; and producing a second human-perceptible indication afterwriting to all of the RFID tags 12A, 12B. Thus, the method can alsoinclude comparing a respective characteristic data string of each of theRFID tags 12A, 12B to a set of identifiers stored in a memory todetermine whether all of the RFID tags 12A, 12B have been written.Alternatively, the method can include writing to a number of other RFIDtags 12A, 12B; producing the first human-perceptible indication afterwriting to each of the RFID tags 12A, 12B; comparing a respectivecharacteristic data string of each of the RFID tags 12A, 12B to a set ofidentifiers stored in a memory to determine if the RFID tag 12A, 12B hasbeen previously written; and producing a second human-perceptibleindication after the number of successive repeatedly written RFID tags12A, 12B exceeds a maximum number of repeated writes. The method canfurther include ceasing to power the radio 44 after writing to the RFIDtag 12A, 12B.

Inclusive Search

The reader 10 can perform an “inclusive” search, such as finding allRFID tags 12A, 12B on a list of RFID tags 12A, 12B. FIG. 11 shows amethod 400 for performing an inclusive search. The user can start theinclusive search 400 by, for example, selecting an appropriate key oricon as in step 402. The microprocessor 46 performs an initialization atstep 404, for example loading a list of characteristic data strings forthe RFID tags 12A, 12B to be located or identified into thecharacteristic data string buffer 49. The list of characteristic datastrings can, for example, be downloaded from the host 23 via interface22. The microprocessor 46 turns ON the radio 44 at step 406.

In step 408, the radio 44 interrogates the RFID tags 12A, 12B to receiveresponse signals containing the respective characteristic data strings.Alternatively, the radio 44 can receive the response signals withoutinterrogating if the RFID tags 12A, 12B are active and periodicallytransmit data without requiring initiation by an interrogation signal.In step 420, the microprocessor 46 compares the received characteristicdata string with the characteristic data strings stored in thecharacteristic data string buffer 49. The microprocessor 46 branches atstep 422, based on the determination of whether the receivedcharacteristic data string corresponds, or matches, any of the storeddata strings.

If the read characteristic data string corresponds to, or matches any ofthe stored characteristic data strings, then one of the RFID tags 12A,12B has been found and the reader 10 reports such to the user and/orhost 23. The reader 10 provides the user indication by activating thespeaker 66 to “beep” in step 414 and activating or “flashing” the GreenRFID related LED 76 in step 416. If the read characteristic data stringdoes not correspond to, or match any of the stored characteristic datastrings, then one of the RFID tags 12A, 12B has not been found, and thereader 10 reports such to the user, and/or host 23. The reader 10provides the user indication by activating the speaker 66 to “click” instep 424 and activating or “flashing” the Red RFID related LED 84 instep 426.

After providing the user indications, the microprocessor determineswhether the reader is finished reading, in step 428. If the reading isfinished, the returned Boolean value (i.e., DONE) causes control to passto an end of the inclusive search routine 400 in step 418. If thereading is not finished, the returned Boolean value (i.e., NOT DONE)causes the radio 22 to continue receiving response signals, passingcontrol to step 418.

Exclusive Search

The reader 10 can perform an “exclusive” search, such as finding anyRFID tags 12A, 12B not on a list of RFID tags 12A, 12B. FIG. 12 shows amethod 500 for performing an exclusive search. The user can start theexclusive search 500 at step 502 by, for example, selecting anappropriate key or icon. The microprocessor 46 performs aninitialization at step 504, for example loading a list of characteristicdata strings for the RFID tags 12A, 12B to be located. At step 506, themicroprocessor turns ON the radio 44.

In step 508, the radio interrogates the RFID tags 12A, 12B to receiveresponse signals containing the respective characteristic data strings.Alternatively, the radio can receive the response signals withoutinterrogating if the RFID tags 12A, 12B are active and periodicallytransmit without requiring an interrogation signal. In step 520, themicroprocessor 46 compares the received characteristic data string withthe characteristic data strings stored in the characteristic data stringbuffer 49. The microprocessor 46 branches at step 566, based on thedetermination of whether the received characteristic data string doesnot correspond, or match, any of the stored data strings.

If the read characteristic data string does not correspond to, or matchany of the stored characteristic data strings, then one of the RFID tags12A, 12B missing from the list has been found, and the reader 10 reportssuch to the user and/or host 23. The reader 10 provides the userindication by activating the speaker 66 to “beep” in step 514, andactivating or “flashing” the Green RFID related LED 76 in step 516. Ifthe read characteristic data string corresponds to, or matches any ofthe stored characteristic data strings, then one of the RFID tags 12A,12B missing from the list has not been found, and the reader 10 reportssuch to the user, and/or host 23. The reader 10 provides the userindication by activating the speaker 66 to “click” in step 524, andactivating or “flashing” the Red RFID related LED 84 in step 526.

After providing the user indications, the microprocessor 46 determineswhether the reader 10 is finished reading, in step 528. If the readingis finished, the returned Boolean value (i.e., DONE) causes control topass to an end of the exclusive search routine 500 in step 518. If thereading is not finished, the returned Boolean value (i.e., NOT DONE)causes the radio to continue receiving response signals, passing controlto step 508.

Association of RFID Tag Data With Item Using Machine-Readable Symbol

Often a user desires to make a physical association between the dataread from one of the RFID tags 12A, 12B and a particular object or item14 (FIG. 1). While the RFID tag 12A, 12B may be attached to, orcontained with the item, it can be difficult to identify the particularRFID tag 12A, 12B that is being read. For example, trying to identifyone or more bags in a cargo hold, or cargo container on an airliner isdifficult and time consuming using only RFID tags 12A, 12B. Each bagwould have to be isolated and the RFID tag 12A, 12B read to ensure thatthe read data came from the RFID tag 12A, 12B associated with theparticular bag. At least one proposed solution involves placinghuman-perceptible indicators on each of the RFID tags, as disclosed inthe commonly assigned U.S. patent application Ser. No. 09/249,359, filedFeb. 12, 1999, entitled, “METHOD AND APPARATUS FOR HUMAN-PERCEPTIBLEIDENTIFICATION OF MEMORY DEVICES, SUCH AS RFID TAGS”. This solution canbe relatively expensive since each RFID tag 12A, 12B requires its ownhuman-perceptible indicator which complicates RFID tag manufacture.

FIG. 13 shows a method 600 of associating the read data from the RFIDtag 12A, 12B with a particular one of the items 14. The associationmethod 600 assumes that an RFID tag 12A, 12B has already been read, acharacteristic data string retrieved and stored, for example, in thecharacteristic data string buffer 49. The user can start the associationmethod 600 in step 602, as discussed generally above. Alternatively, thereader 10 can be configured to automatically start the associationmethod 600 at step 602. In step 668, the microprocessor 46 enters thesymbol reading mode. The user activates the trigger 20 in step 670,causing the microprocessor 46 to activate the image sensor 52 to readthe machine-readable symbol 24A, 24B at which the reader 10 is directed.In step 672, the image sensor 52 acquires data from the machine-readablesymbol 24A, 24B by scanning, digitizing, or by any commonly knownmethods in the relevant art. As part of acquiring the data, themicroprocessor 46, or a dedicated processor (not shown), decodes theimage to acquire a characteristic data string encoded in themachine-readable symbol 24A, 24B. Methods and apparatus for acquiringdata from machine-readable symbols are commonly known in the art, andare specifically taught in The Bar Code Handbook 3^(rd) Ed, by Palmer,Roger C, Helmers Publishing, Inc. (ISBN 0-911261-09-5), and, in theinterest of brevity, will not be described in further detail.

To determine whether the machine-readable symbol 24A, 24B that thereader 10 is pointing at is associated with the RFID tag data read bythe reader 10, the microprocessor 46 compares a characteristic datastring read from the RFID tag 12A, 12B with the characteristic datastring read from the machine-readable symbol 24A, 24B, in step 620. Theuser can visually associate the RFID tag 12A, 12B with themachine-readable symbol 24A, 24B since the RFID tag 12A includes themachine-readable symbol 24A, or the RFID tag 12B and machine-readablesymbol 24B are carried by the same item 14, or can be visuallyassociated is some other manner. The user can therefore determine thatthe data is from a particular RFID tag 12A, 12B when a match isindicated by the reader 10.

If the characteristic data string from the machine-readable symbol 24A,24B corresponds to, or matches, the characteristic data string from theRFID tag 12A,12B, the reader 10 provides an indication that anassociation exists. To provide the indication, the microprocessor 46activates the speaker 66 to emit a single “beep” in step 614 andactivates or “flashes” the Green RFID related LED 76 and the Greensymbol related LED 78 in step 674. The RFID related and the symbolrelated LEDs 76, 78 are each activated, indicating that both an RFID tag12A, 12B and a machine-readable symbol 24A, 24B have been located,providing a consistency across the user interface.

In step 676, the microprocessor 46 can turn OFF the image sensor 52after having found an association. In step 612, the reader 10 can reportthe data, for example transmitting the RFID data to the host 23 via thecommunications port 38 and interface 22. In step 676, the reader 10 canreceive a direction or command from the host 23 via the interface 22 andthe communications port 38. In step 678, the microprocessor 46determines whether the buffer should be modified based on the commandfrom the host 23. If the buffer is to be modified, the microprocessor 46modifies the buffer at step 680, and passes control to an end of theassociation method 600 in step 618. Otherwise, the microprocessor 46passes control directly to the end of the association method, in step600, without modifying the buffer.

If the characteristic data string from the machine-readable symbol 24A,24B does not correspond to, or match the characteristic data string fromthe RFID tag 12A, 12B, the reader 10 provides an indication that anassociation does not exist. To provide the indication, themicroprocessor 46 activates the speaker 66 to emit a three “Beeps” instep 682, and activates or “flashes” the Red RFID related LED 84 and theGreen symbol related LED 78 in steps 626, 684, respectively. The Greensymbol related LED 78 is flashed to indicate that a symbol has beensuccessfully read, while the Red RFID related 84 is flashed to indicatethat the data is not associated with the machine-readable symbol 24A,24B, further providing consistency across the user interface. Themicroprocessor 46 proceeds to the end of the method 600, in step 618.

Automatically Reading A Symbol Based On Proximity To RFID Tag, orFrequency of RFID Tag's Responses

FIG. 14 shows a method 700, in which the reader 10 automatically readsthe machine-readable symbol when the reader 10 is within a definedproximity of the RFID tag 12A, and hence within the defined proximity ofthe machine-readable symbol 24A. The automated symbol reading featureprovides numerous benefits, for example the automated symbol readingfeature can simplify operation of the reader, and/or reduce theprobability of user error. The automated symbol reading feature can alsoreduce the amount of labor required to operate the reader 10, and caneven eliminate the need for a human operator. The method 700 of FIG. 14can be used as part of, or with, many of the previously describedmethods.

The antenna 42 in the reader 10 can be directionally sensitive. Thedirectionally sensitive antenna 42 has a directional range, in otherwords, the antenna is more sensitive in certain directions than otherdirections. As the reader 10 approaches a particular RFID tag 12A, 12B,that RFID tag 12A, 12B spends a higher percentage of time within therange of the reader 10. In contrast, other RFID tags 12A, 12B are in therange a lower percentage of time. Thus, as the reader 10 comes within apredefined proximity of the RFID tag 12A, 12B, the number of “hits”(i.e., reading an RFID tag having a desired characteristic data string)will increase, and the number of “misses” (i.e., reading RFID tags nothaving the desired characteristic data string) will decrease. The usermay recognize this from an increase in the number of “Beeps” and adecrease in the number of “Clicks” emitted by the reader 10. Themicroprocessor 46 in the reader 10, can keep track of the number of hitsand the number of misses for some unit length of time, steps 786, 788,respectively. The microprocessor 46 can determine a ratio of the numberof hits per unit of time and the number of misses per unit of time.Alternatively, the host 23 can process the same information.

In step 790, the microprocessor 46 determines whether the ratio of hitsto misses exceeds a symbol reading threshold. If the ratio does notexceed the symbol reading threshold, the microprocessor 46 returns tostep 786 and the reader 10 continues to read the RFID tags 12A, 12B,continually revising and checking the ratio against the threshold.

If the ratio exceeds the symbol reading threshold, the microprocessor 46turns the image sensor 52 ON, for example, switching from the RFIDreading mode to the symbol reading mode in step 768. The microprocessor46 controls the image sensor 52 to image and decode the machine-readablesymbol 24A, 24B in 772. In step 774, the microprocessor 46 turns theimage sensor 52 OFF, thereby conserving power. In step 720, themicroprocessor 46 compares the characteristic data string from themachine-readable symbol 24A, 24B to the characteristic data string fromthe RFID tag 12A, 12B.

If the characteristic data string from the machine-readable symbol 24A,24B corresponds to, or matches, the characteristic data string from theRFID tag 12A,12B, the reader 10 provides an indication that anassociation exists. To provide the indication, the microprocessor 46activates the speaker 66 to emit a single “Beep” in step 714 andactivates or “flashes” the Green RFID related LED 76 and the Greensymbol related LED 78 in step 774. The RFID related and the symbolrelated LEDs 76, 78 are each activated, indicating that both an RFID tag12A, 12B and a machinereadable symbol 24A, 24B have been located,providing a consistency across the user interface.

In 712, the reader 10 can report the data, for example automaticallytransmitting the RFID data to the host 23 via the communications port 38and interface 22. In step 776, the reader 10 can receive a direction orcommand from the host 23 via the interface 22 and the communicationsport 38. In step 778, the microprocessor 46 determines whether thecharacteristic data string buffer 49 should be modified based on thecommand from the host 23. If the buffer 49 is to be modified, themicroprocessor 46 modifies the buffer at step 780, and passes control toan end of the association method 700 at step 718. Otherwise, themicroprocessor 46 passes control directly to the end of the associationmethod 700 at step 718 without modifying the characteristic data stringbuffer 49.

If the characteristic data string from the machine-readable symbol 24A,24B does not correspond to, or match the characteristic data string fromthe RFID tag 12A, 12B, the reader 10 provides an indication that theassociation does not exist. The microprocessor 46 activates the speaker66 to emit three “Beeps” in step 782, and activates or “flashes” theGreen symbol related LED 78 and the Red RFID related LED 84 in steps 784and 726, respectively. The Green symbol related LED 78 is flashed toindicate that a symbol has been successfully read, while the Red RFIDrelated 84 is flashed to indicate that the data is not associated withthe machine-readable symbol 24A, 24B, further providing consistencyacross the user interface.

SUMMARY

The various embodiments described above can be combined to providefurther embodiments. All of the above U.S. patents, patent applicationsand publications referred to in this specification are incorporated byreference. Aspects of the invention can be modified, if necessary, toemploy systems, circuits and concepts of the various patents,applications and publications to provide yet further embodiments of theinvention.

Although specific embodiments of and examples data carrier readers andreading are described herein for illustrative purposes, variousequivalent modifications can be made without departing from the spiritand scope of the invention, as will be recognized by those skilled inthe relevant art. The teachings provided herein of the invention can beapplied to any data carrier reader, not necessarily the exemplarycombination RFID tag and symbol reader generally described above.

For example, some of the structures and methods can be used with readerscapable of reading only RFID tags. Some of the structures and methodscan be used with readers capable of reading only machine-readablesymbols. Some of the structures and methods can be suitable with readersfor other data carriers, such as optical tags and touch memory devices.The methods and structures are generally applicable with other wirelessmemory devices, not just radio frequency, and the term RFID as usedherein is meant encompass wireless memory devices operating in allranges of the electromagnetic spectrum, not only the radio frequencyportion. Similarly, the structures and methods disclosed can work withany variety of modulation techniques, including, but not limited to,amplitude modulation, frequency modulation, phase modulation and/orpulse width modulation. The structures and methods can also be appliedto various machine-readable symbologies, including, but not limited to,bar codes, stacked codes, area and/or matrix codes. The image sensor 52can be any type of image capture device, including laser scanners, one-and two-dimensional charged coupled devices, Vidicons, and the like.

These and other changes can be made to the invention in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the invention to thespecific embodiments disclosed in the specification and the claims, butshould be construed to include all apparatus and methods that operate inaccordance with the claims. Accordingly, the invention is not limited bythe disclosure, but instead its scope is to be determined entirely bythe following claims.

We claim:
 1. A method of operating a data carrier reader, comprising:receiving a plurality of characteristic data strings from each of anumber of RFID tags, including at least one RFID tag of interest;comparing at least a portion of each of the received characteristic datastrings to at least one identifier stored in a buffer, the identifiercorresponding to the RFID tag of interest; producing a firsthuman-perceptible indication in response to the number of receivedcharacteristic data strings that correspond to the at least oneidentifier; and automatically operating a symbol reader when a rate ofresponse corresponding to the at least one identifier exceeds athreshold value.
 2. The method of claim 1, further comprising: producinga second human-perceptible indication in response to the number ofreceived characteristic data strings that do not correspond to the atlast one identifier.
 3. The method of claim 1, further comprising:producing a second human-perceptible indication in response to thenumber of received characteristic data strings that do not correspond tothe at last one identifier, wherein the first human-perceptibleindication is a first sound and the second human-perceptible indicationis a second sound, different from the first sound.
 4. The method ofclaim 1, further comprising: determining a hit rate of responsecorresponding to a number of received characteristic data strings thatcorrespond to the at least one identifier; determining a miss rate ofresponse corresponding to the number of received characteristic datastrings that do not correspond to the at least one identifier; anddetermining the threshold value from the hit rate of response and themiss rate of response.
 5. The method of claim 1, further comprising:reading a symbol; and comparing at least a portion of the read symbol tothe at least one identifier stored in a buffer.
 6. The method of claim1, further comprising: reading a symbol; comparing at least a portion ofthe read symbol to the at least one identifier stored in a buffer; andautomatically ceasing to power the symbol reader after reading thesymbol.
 7. The method of claim 1, further comprising: reading a symbol;comparing at least a portion of the read symbol to the at least oneidentifier stored in a buffer; and automatically transferring thecharacteristic data string read from the RFID tag of interest to a hostif the at least a portion of the read symbol corresponds to the at leastone identifier stored in a buffer.
 8. A method of operating a datacarrier reader, comprising: receiving a plurality of responses from anumber of RFID tags including at least one RFID tag of interest; andautomatically operating a symbol reader when a rate of the responsesfrom the RFID tag of interest exceeds a threshold rate of response. 9.The method of claim 8, further comprising: producing a firsthuman-perceptible indication corresponding to a number of the responsesreceived from the RFID tag of interest.
 10. The method of claim 8,further comprising: producing a first human-perceptible indicationcorresponding to a number of the responses received from the RFID tag ofinterest; and producing a second human-perceptible indication inresponse to a number of the responses received from the RFID tags otherthan the RFID tag of interest.
 11. The method of claim 8, furthercomprising: determining the threshold rate of response from the ratio ofthe responses of the RFID tags other than the RFID tag of interest andthe responses of the RFID tag of interest.
 12. The method of claim 8,further comprising: reading a symbol; and comparing at least a portionof the read symbol to at least a portion of at least one of theplurality of responses.
 13. The method of claim 8, further comprising:reading a symbol; comparing at least a portion of the read symbol to atleast a portion of at least one of the plurality of responses; andautomatically ceasing to power the symbol reader after reading thesymbol.
 14. The method of claim 8, further comprising: reading a symbol;comparing at least a portion of the read symbol to at least a portion ofat least one of the plurality of responses; and automaticallytransferring at least a portion of the response received from the RFIDtag of interest to a host if the at least a portion of the read symbolcorresponds to the at least a portion of the at least one of theplurality of responses.